Echocardiographic Assessment of Septal and Posterior Wall Dynamics and their Effect on Left Ventricular Filling in Idiopathic Hypertrophic Subaortic Stenosis
M-mode echocardiography has been invaluable in the diagnosis of idiopathic hypertrophic subaortic stenosis (IHSS), but assessment of left ventricular (LV) function has been limited to measurement of LV cavity size, ejection fraction, and velocity of fiber shortening (Vcf). In this study, computerized analysis of echocardiography was used to assess LV function in patients with IHSS in terms of septal (VS), posterior wall (PW), and LV cavity dynamics throughout the cardiac cycle, with particular emphasis on wall movement during diastole. In addition, the relations between wall dynamics, LV filling, mitral valve opening, and clinical symptomatology were investigated. LV echograms of both sides of the septum and of the endocardium and epicardium of the posterior LV wall were obtained at the level of the posterior mitral valve leaflet in 29 patients with IHSS (aged 16–69 years) and 20 normal subjects (aged 19–63 years). Echograms were digitized and processed by a CDC 3500 computing system to provide plots of instantaneous LV cavity dimension (D) and VS and PW thickness. Measurements were made of peak rate of increase in minor LV dimension (dD/dt); duration of the rapid LV filling phase (time from dD/dt = 0 to the time dD/dt had decreased to 20% of its peak value, which corresponds to the discontinuity on the plot of instantaneous LV dimension); peak shortening rate (dD/dt·1/D, or Vcf); and normalized peak rates of change of VS and PW thickness (d[VS]/dt.1/VS and d[PW]/dt·1/PW) in systole and diastole.